tvrepairinfo.com In this video I show the importance of measuring the current or the power your TV is using as a way of determining if there are any shorted parts. I also show the value of using a variac transformer to find shorted circuits before you apply full power. Ifyour a professional looking for more understanding on how repair LCD TVs or an electronics hobbyist here are some great resources. Troubleshooting & Repairing LCD TVs by John Preher at http For someone new to electronics the first few pages of this book may be a bit challenging but the majority of this book is easy reading with lots of pictures,diagrams and useful troubleshooting techniques. Johns book gives you a good idea about the main test points you should look for and their approximate voltages. ======================================== How to troubleshoot and repair Switch Mode Power supplies by Jestine Yong at davestv.jestinemichellepow.click2sell.eu This book is a bit spendy but I’m still glad I purchased it. In my opinion it’s a must read. Jestine is good at getting right to the main points you need to understand about troubleshooting this kind of power supply and its associated feedback circuits. Since a majority of the problems I have seen on LCD TVs are related to bad power supplies I figured it will pay for itself many times over. Most of the book was easy reading with plenty of pictures and diagrams. ======================================== Testing electronic components and finding unknown …
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You sir, are a wealth of knowledge.
@GrantsPassTVRepairs Now that I think about it it makes more sense, all metals have resistivity and if ALL the current went through the coils in the meter the coils would have to be humongous to carry all that current. It makes sense to only want to have only a small amount of current to pass through the coil to give you a reading. I learned something new. Thanks!
@GrantsPassTVRepairs So even though there is a short since the meter is so low in resistance some electrons may pass through anyway? I know if two wires are in parellel current will go through both wires, is it something similar with an ammeter?
@bandet888 The meter is so sensitive it still works with a short/shunt across it. The size of the shunt determines how sensitive the meter is. The same meter which is designed to measure up to 5 amps could also measure 50 amps or 500 amps with a larger shunt. I hope this helps.
If you have a dead short between the terminals of an amp meter why would electrons pass through the meter? I’m sure the meter has ALMOST 0 ohms but can’t be totaly 0 ohms as the meter needs to absorb SOME power to give you a reading. How can a meter absorb any (even minute) power if there is a dead shour across the terminals? Or can it work the same as the meter an electrition uses but then you don’t even need any terminals.
Clearly understood grant!!Thanks
I learnt lot of tips from your videos, thank you very much for shearing
The new bulbs worked and my tv problem is solved.
This inspired my to attempt to fix another samsung LCD with a slightly different problem. This tv has normal backlight and sound, but no picture. After powering on, the LCD is a dark grey color and slowly begins to fade to an all white screen. When i change the input source, the screen flashes and the transformer on the PCB starts humming. Also the led on the front is constantly blinking. Any ideas on this one?
the best you tube site I ever found?
keep up the good work… you happen to have block diagram how lcd-plasma tv works?
Sounds like your making great progress.
I reassembled the TV without the LCD panel, so I could see the lamps fire up. It turns out that one bulb is not lighting. I should have done this from the beginning. I have a nice picture of it, if you’d like to see.
Also I reassembled the tv without the lcd panel, so I could see exactly which bulb wasnt firing. Turns out it is the 3rd bulb from the top. I got a nice picture of it too if you’d like to see it. I should have done this before I bought the inverter. I think Ill just buy 2-3 bulbs and replace the ones that look like they’ll burnout next. I got a quote from ccflwarehouse for $12.95 a bulb. which was lower than $19.99 i found at 2 other sites. Ill follow up with the results
I bought a replacement inverter on ebay, but I got the same results, 1 second of backlight. I was able to return it, so I will buy some new ccfls and see if that fixes it.
Yeah he’s right. One bulb can throw off the inverter, remove the CCFL’s and one… maybe two will probably be really black on the ends. But, if you’re in there and replacing lamps you should probably do all of them
I would start by testing them on while they are soldered on the inverter board to see if its open or has real high resistance
Can I test them while they are still in the board?
Yes there is. Using your volt ohm meter you can put it on the resistance scale, and measure across the primary and secondary side to see it its open and or has any shorts. Since you may not know what the resistance should be, try measuring some of the other inverter transformers, and see how they read in comparison.
If you had what’s know as a ring tester that
is there a test I can try on the inverter transformers?
One additional thought. It could also be that just one of the inverter transformers has gone bad, and or the related circuitry which drives them. but they might not sell you a single transformer anyway. I have not repaired enough LCD sets to tell you which is more likely to be bad between the inverter board and the lights.
I can’t speak for every design, but I was told many of them have feedback circuits which turn off the whole set when one of the lights has a problem.
Also, if it is the CCFLs, do they all go bad at once? or could one bulb be the cause for the other 11 not to power on? Is it a series or parallel circuit? would I need to buy 12 new ones or just a few of them?
In your experience with samsung lcds, what part is more likely to be the faulty part? the inverter or the CCFLs?
Ive found both parts online, but I dont know which part I should pursue. CCFLs – $10 to 12 a piece. Inverter board $70. I got the bad TV from my dad, who was going to throw it out, so if I can spend about $100 and a few hours to get it running again, Id say its worth it.
Thanks
That trick with the hair dryer will not work if the capacitors are to far gone. Since you may not be able to get parts on your TV any way, it might be fun to see what kind of back light you can come up with on your own such as LEDs. I recently saw a youtube video on this. Perhaps more work than the TV is worth, but if your the experimental type it might make a fun project.
I’ve verified that the LCD is working after that one second of backlight using the flashlight trick. Im getting normal audio as well. After watching the video on capacitors, I tried the hairdryer trick on the 4 caps on the inverter board. I heated them up before turning the tv on, but the heated caps didnt do the trick. Also I tested the voltage to the inverter board and its reading 24.4V. According to a samsung troubleshooting guide on this model, its needs to be 24V. Thanks for the quick post
You can shine a light of your own behind the screen and see if your picture is there. That will at least confirm if there are additional problems other than the light circuit, but because of the way the feedback circuit works sometimes its hard to draw the dotted lines between the symptom and the cause.